6 or 7

Teacher: If I gave you 2 rabbits, and another 2 rabbits and another 2, how many will you have?
Johnny: Seven Sir
Teacher: No, listen carefully. If I gave you 2 rabbits, and another 2 rabbits and another 2, how many will you have?
Johnny: Seven
Teacher: Let me put it to you differently. If I gave you 2 apples, and another 2 apples and another 2, how many will you have?
Johnny: Six.
Teacher: Good. Now if I gave you 2 rabbits, and another 2 rabbits and another 2, how many will you have?
Johnny: Seven!
Teacher: Where do you get seven from?
Johnny: Because I have already one rabbit at home..